The present disclosure relates generally to monitoring movement of a human eye.
Drowsiness and fatigue while driving is a serious problem that leads to thousands of automobile crashes each year. Critical aspects of driving impairment associated with sleepiness include reaction time, attention, and information processing. Sleep related crashes are most common in young people, shift workers whose sleep is disrupted by working at night or working long or irregular hours, and people with untreated sleep apnea syndrome and narcolepsy.
There are some in-vehicle systems that are intended to measure sleepiness or some behavior associated with sleepiness in commercial and noncommercial driving. Examples include brain wave monitors, eye-closure monitors, devices that detect steering variance, and tracking devices that detect lane drift. For example, infrared cameras or other devices have been used to monitor a driver's awareness. These devices are typically mounted on the dashboard or roof of the driver's vehicle. Such devices, however, require that the driver maintain constant eye contact with the camera. In addition, they do not monitor eyelid movement if the user looks sideways or turns around. These cameras may also have difficulty seeing through eyeglasses or sunglasses and may not operate effectively in sunlight.
In addition to monitoring drowsiness of drivers, such systems are also needed for monitoring pilots or other individuals. One system that is independent from the vehicle is an eye movement monitoring system which is contained within a frame worn on a user's head. An example of this type of system is disclosed in U.S. Patent Application Publication No. US2001/0028309 A1, by William C. Torch. The system includes an array of emitters for directing light towards a person's eye and an array of sensors for detecting light from the array of emitters. The sensors detect light that is reflected off of the eye or eyelid, thus producing output signals indicating when the eye is covered by the eyelid. The emitters project a reference frame towards the eye, and a camera on the frame monitors movement of the eye relative to the reference frame. Such systems, however, are typically large, complex, and costly to manufacture. Furthermore, these systems may obstruct at least a portion of the user's view.
Eye monitoring systems are also used to track a user's eye to control electrical devices such as a computer input device (e.g., pointer or mouse) and for assistive technology for disability products. There are many different techniques which can be used for eye tracking. One conventional system is a remote mounted tracking device. A major drawback to this type of system is that it is not very effective when the user is actively moving their head or body independent of gazing at a point. Conventional head mounted eye tracking devices often require complex optics and processing equipment and are typically expensive to manufacture, heavy, making them difficult to wear for extended periods of time, and often obstruct at least a portion of a user's view.